Abstract

Speckle patterns produced by random optical fields with two (or more) widely different correlation lengths exhibit speckle spots that are themselves highly speckled. Using computer simulations and analytic theory we present results for the point singularities of speckled speckle fields, namely, optical vortices in scalar (one polarization component) fields and C points in vector (two polarization components) fields. In single correlation length fields both types of singularities tend to be more or less uniformly distributed. In contrast, the singularity structure of speckled speckle is anomalous; for some sets of source parameters vortices and C points tend to form widely separated giant clusters, for other parameter sets these singularities tend to form chains that surround large empty regions. The critical point statistics of speckled speckle is also anomalous. In scalar (vector) single correlation length fields phase (azimuthal) extrema are always outnumbered by vortices (C points). In contrast, in speckled speckle fields, phase extrema can outnumber vortices and azimuthal extrema can outnumber C points by factors that can easily exceed 104 for experimentally realistic source parameters.

Figures (2)

Scalar speckle. Shown are simulations for disks with a=1 and b=100. In (a) and (b) Ib=0, which yields familiar single Λ speckle with Λ∼1. In (c)–(g) Ib∕Ia=2⋅10−6(K=0.02), which yields speckled speckle with Λa∼1 and Λb∼0.01. (a) Intensity of single Λ speckle, (b) phase map corresponding to (a), (c) intensity of speckled speckle, (d) phase map corresponding to (c), (e)–(f) forty-fold enlargements of the regions in (d) pointed to by the arrows labeled e, f, and g. Here and throughout the intensity (phase) is coded increasing (0 to 2π) black to white, and positive (negative) vortices are shown by white circles with black rims and black circles with white rims.

Vector field speckled speckle. Shown are simulations for disks with a=1, b=10, Ib∕Ia=3⋅10−3(K=0.3). (a) Intensity, (b) phase Φ12 of complex Stokes field S12, (c) enlargement of the black–white band on the horizontal centerline in (b), (d)–(f) enlargement of the region beneath the black–white band in (b), (d) phase Φ12 of S12, (e) phase −ΦR of ER, and (f) phase ΦL of EL.